001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.eclipse.aether.util.graph.manager;
020
021import java.util.ArrayList;
022import java.util.Collection;
023import java.util.HashMap;
024
025/**
026 * Warning: this is a special map-like construct that suits only and should be used only in this package!
027 * It has the following properties:
028 * <ul>
029 *     <li>memorizes once calculated hashCode</li>
030 *     <li>once hashCode calculated, goes into "read only" mode (put method will fail)</li>
031 *     <li>otherwise all the rest is same as for {@link HashMap}</li>
032 * </ul>
033 *
034 * This class is not a generic map class; only those methods are "protected" that are in use in this very
035 * package.
036 *
037 * @param <K>
038 * @param <V>
039 */
040public class MMap<K, V> {
041    private static final MMap<?, ?> EMPTY_MAP = new MMap<>(new HashMap<>(0)).done();
042
043    @SuppressWarnings("unchecked")
044    public static <K, V> MMap<K, V> empty() {
045        return (MMap<K, V>) MMap.EMPTY_MAP;
046    }
047
048    public static <K, V> MMap<K, V> copy(MMap<K, V> orig) {
049        return new MMap<>(new HashMap<>(orig.delegate));
050    }
051
052    public static <K, V> MMap<K, Collection<V>> copyWithKey(K key, MMap<K, Collection<V>> orig) {
053        HashMap<K, Collection<V>> delegateLocal = new HashMap<>(orig.delegate);
054        delegateLocal.computeIfPresent(key, (k, v) -> new ArrayList<>(v));
055        return new MMap<>(delegateLocal);
056    }
057
058    protected final HashMap<K, V> delegate;
059
060    private MMap(HashMap<K, V> delegate) {
061        this.delegate = delegate;
062    }
063
064    public boolean containsKey(K key) {
065        return delegate.containsKey(key);
066    }
067
068    public V get(K key) {
069        return delegate.get(key);
070    }
071
072    public V put(K key, V value) {
073        return delegate.put(key, value);
074    }
075
076    public MMap<K, V> done() {
077        return new DoneMMap<>(delegate);
078    }
079
080    @Override
081    public int hashCode() {
082        throw new IllegalStateException("MMap is not done yet");
083    }
084
085    @Override
086    public boolean equals(Object o) {
087        throw new IllegalStateException("MMap is not done yet");
088    }
089
090    private static class DoneMMap<K, V> extends MMap<K, V> {
091        private final int hashCode;
092
093        private DoneMMap(HashMap<K, V> delegate) {
094            super(delegate);
095            this.hashCode = delegate.hashCode();
096        }
097
098        @Override
099        public V put(K key, V value) {
100            throw new IllegalStateException("Done MMap is immutable");
101        }
102
103        @Override
104        public MMap<K, V> done() {
105            return this;
106        }
107
108        @Override
109        public int hashCode() {
110            return hashCode;
111        }
112
113        @Override
114        public boolean equals(Object o) {
115            if (!(o instanceof MMap)) {
116                return false;
117            }
118            MMap<?, ?> other = (MMap<?, ?>) o;
119            return delegate.equals(other.delegate);
120        }
121    }
122}